This application relates generally to the field of vehicle suspensions, and more particularly, to monitoring and adjusting tire pressure of a vehicle.
Dual rear tire vehicles such as super duty dually trucks or trailers experience extremely variable loads. At times, the vehicle may be operated without any load at all, while at other times the load may include cargo or passengers, in varying amount or number. Owing to the distribution of load dictated by vehicle design, the load carried by rear axle tends to be greater than the load carried by front axle. Thus, rear tires, having inner and outer tires, generally require higher pressures than front tires for optimal operation with the load. Manufacturers typically provide placards, attached to the vehicle, depicting optimal tire pressure values under varying load conditions. The placards recommend a lower front tire pressure than the rear tire pressure under maximum load conditions. In addition, two pressure levels will be recommended for the rear tires, a lower pressure for comfort and handling under lighter load conditions, and a higher pressure to accommodate heavier loads. This system is generally referred to as a “dual placard” or “split placard” system.
The dual rear tire vehicle requires a Tire Pressure Monitoring System (TPMS) to warn a vehicle operator if the tire pressures of each of the front and rear tires are below a predetermined threshold value. The TPMS may be a remote tire pressure monitoring system including remote tire pressure sensors, monitoring absolute tire pressures, and a centralized receiver. The individual tire pressures are communicated to the central receiver via radio frequency transmitters, which alerts the vehicle operator whether the pressure is below a predetermined limit. The alert may be in form of an alarm or in form of a display on a touch screen. In some systems, the alert can be generic and simply inform the vehicle operator that at least one of the tires has low pressure. Alternatively, the alert can specifically indicate the running tire having low pressure.
Typically, the rear tires have a different predetermined threshold value relative to the front tires. To ensure that correct tire pressures are communicated to the central receiver, the TPMS needs to differentiate between the front and dual rear tire locations. Further, a differentiation between inner rear tire and outer rear tires is required. Accordingly, appropriate identification of the tire locations becomes critical. For the appropriate identification, each tire pressure sensors include an associated unique identification code. Using such identification, the receiver associates each tire pressure with a particular tire location. In the event of a routine maintenance procedure or a repair procedure, however, when the tires are removed from the vehicle and placed back, the tire positions could change from front to rear or vise versa. This may result in communication of incorrect tire positions to the receiver.
To rectify the problem mentioned above, there are manual processes that can be used to calibrate the TPMS with the proper position of each tire. It should be apparent, however, that manual calibration processes may be subjected to human error. As a result, the manual process may lead to incorrect recognition of tire locations. In addition, the existing TPMS may not be capable of differentiating between the inner and outer rear tires of the dual rear tire vehicle.
It is evident that there remains a need for efficiently identifying position of each tire of a dual rear tire vehicle in order to maintain tire pressures within recommended ranges.